Rework and repair of components in a solar cell array

ABSTRACT

A substrate for solar cells is configured such that an area of the substrate remains exposed when at least one solar cell having at least one cropped corner that defines a corner region is attached to the substrate, one or more electrical connections for the solar cell are made in the corner region resulting from the cropped corner of the solar cell, and at least one of the electrical connections, connecting a first interconnect in a first location, is repaired by connecting a second interconnect in a second location in the at least one of the electrical connections different from the first location.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 119(e) ofthe following co-pending and commonly-assigned applications:

U.S. Provisional Application Ser. No. 62/394,636, filed on Sep. 14,2016, by Eric Rehder, entitled “SOLAR CELL ARRAY CONNECTIONS,”attorneys' docket number 16-0878-US-PSP (G&C 147.211-US-P1);

U.S. Provisional Application Ser. No. 62/394,616, filed on Sep. 14,2016, by Eric Rehder, entitled “CORNER CONNECTORS FOR A SOLAR CELLARRAY,” attorneys' docket number 16-0435-US-PSP (G&C 147.212-US-P1);

U.S. Provisional Application Ser. No. 62/394,623, filed on Sep. 14,2016, by Eric Rehder, entitled “PREFABRICATED CONDUCTORS ON A SUBSTRATETO FACILITATE CORNER CONNECTIONS FOR A SOLAR CELL ARRAY,” attorneys'docket number 16-0436-US-PSP (G&C 147.213-US-P1);

U.S. Provisional Application Ser. No. 62/394,627, filed on Sep. 14,2016, by Eric Rehder, entitled “SELECT CURRENT PATHWAYS IN A SOLARARRAY,” attorneys' docket number 16-0437-US-PSP (G&C 147.214-US-P1);

U.S. Provisional Application Ser. No. 62/394,629, filed on Sep. 14,2016, by Eric Rehder, entitled “MULTILAYER CONDUCTORS IN A SOLAR ARRAY,”attorneys' docket number 16-0438-US-PSP (G&C 147.215-US-P1);

U.S. Provisional Application Ser. No. 62/394,632, filed on Sep. 14,2016, by Eric Rehder, entitled “REWORK AND REPAIR OF COMPONENTS IN ASOLAR ARRAY,” attorneys' docket number 16-0439-US-PSP (G&C147.216-US-P1);

U.S. Provisional Application Ser. No. 62/394,649, filed on Sep. 14,2016, by Eric Rehder, entitled “POWER ROUTING MODULE FOR A SOLAR ARRAY,”attorneys' docket number 16-0440-US-PSP (G&C 147.217-US-P1);

U.S. Provisional Application Ser. No. 62/394,666, filed on Sep. 14,2016, by Eric Rehder, entitled “POWER ROUTING MODULE WITH A SWITCHINGMATRIX FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0441-US-PSP(G&C 147.218-US-P1);

U.S. Provisional Application Ser. No. 62/394,667, filed on Sep. 14,2016, by Eric Rehder, entitled “NANO-METAL CONNECTIONS FOR A SOLAR CELLARRAY,” attorneys' docket number 16-0442-US-PSP (G&C 147.219-US-P1);

U.S. Provisional Application Ser. No. 62/394,371, filed on Sep. 14,2016, by Eric Rehder, entitled “BACK CONTACTS FOR A SOLAR CELL ARRAY,”attorneys' docket number 16-0443-US-PSP (G&C 147.220-US-P1);

U.S. Provisional Application Ser. No. 62/394,641, filed on Sep. 14,2016, by Eric Rehder, entitled “PRINTED CONDUCTORS IN A SOLAR CELLARRAY,” attorneys' docket number 16-0614-US-PSP (G&C 147.228-US-P1); and

U.S. Provisional Application Ser. No. 62/394,672, filed on Sep. 14,2016, by Eric Rehder, Philip Chiu, Tom Crocker and Daniel Law, entitled“SOLAR CELLS FOR A SOLAR CELL ARRAY,” attorneys' docket number16-2067-US-PSP (G&C 147.229-US-P1);

all of which applications are incorporated by reference herein.

This application claims the benefit under 35 U.S.C. Section 120 of thefollowing co-pending and commonly-assigned applications:

U.S. Utility application Ser. No. ______, filed on same date herewith,by Eric Rehder, entitled “SOLAR CELL ARRAY CONNECTIONS USING CORNERCONDUCTORS,” attorneys' docket number 16-0878-US-NP (G&C 147.211-US-U1);

U.S. Utility application Ser. No. ______, filed on same date herewith,by Eric Rehder, entitled “PREFABRICATED CONDUCTORS ON A SUBSTRATE TOFACILITATE CORNER CONNECTIONS FOR A SOLAR CELL ARRAY,” attorneys' docketnumber 16-0436-US-NP (G&C 147.213-US-U1);

U.S. Utility application Ser. No. ______, filed on same date herewith,by Eric Rehder, entitled “POWER ROUTING MODULE FOR A SOLAR ARRAY,”attorneys' docket number 16-0440-US-NP (G&C 147.217-US-U1);

U.S. Utility application Ser. No. ______, filed on same date herewith,by Eric Rehder, entitled “POWER ROUTING MODULE WITH A SWITCHING MATRIXFOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0441-US-NP (G&C147.218-US-U1);

U.S. Utility application Ser. No. ______, filed on same date herewith,by Eric Rehder, entitled “NANO-METAL CONNECTIONS FOR A SOLAR CELLARRAY,” attorneys' docket number 16-0442-US-NP (G&C 147.219-US-U1); and

U.S. Utility application Ser. No. ______, filed on same date herewith,by Eric Rehder, Philip Chiu, Tom Crocker, Daniel Law and Dale Waterman,entitled “SOLAR CELLS FOR A SOLAR CELL ARRAY,” attorneys' docket number16-2067-US-NP (G&C 147.229-US-U1);

all of which applications claim the benefit under 35 U.S.C. Section119(e) of the co-pending and commonly-assigned provisional applicationslisted above: 62/394,636; 62/394,616; 62/394,623; 62/239,627;62/394,629; 62/394,632; 62/394,649; 62/934,666; 62/394,667; 62/694,371;62/394,641; and 62/394,672; and

all of which applications are incorporated by reference herein.

BACKGROUND INFORMATION 1. Field

The disclosure is related generally to solar cell panels and, morespecifically, to rework and repair of components in a solar cell array.

2. Background

Typical spaceflight-capable solar cell panel assembly involves buildinglong strings of solar cells. These strings are variable in length andcan be very long, for example, up to and greater than 20 cells.Assembling such long, variable, and fragile materials is difficult,which has prevented automation of the assembly.

Existing solutions use solar cells assembled into CIC (cell,interconnect and coverglass) units. The CIC has metal foil interconnectsconnected to the front of the cell that extend in parallel from one sideof the CIC. The CICs are located close to each other and theinterconnects make connection to the bottom of an adjacent cell. Usingthese interconnects, the CICs are assembled into linear strings. Theselinear strings are built-up manually and then laid out to form a largesolar cell array comprised of many strings of variable length.

Additionally, a bypass diode is used to protect the cells from reversebias, when the cells become partially shadowed. The bypass diodegenerally connects the back contacts of two adjacent cells within thesolar cell array.

When used in a satellite, the solar cell array is typically packaged asa panel. The dimensions of the panel are dictated by the needs of thesatellite, including such constraints as needed power, as well as thesize and shape necessary to pack and store the satellite in a launchvehicle. Furthermore, the deployment of the panel often requires thatsome portions of the panel are used for the mechanical fixtures and thesolar cell array must avoid these locations. In practice, the panel isgenerally rectangular, but its dimensions and aspect ratio vary greatly.The layout of the CICs and strings to fill this space must be highlycustomized for maximum power generation, which results in a solar panelfabrication process that is highly manual.

What is needed, then, is a means for promoting automated manufacturingof solar arrays, while preserving the ability for customization of solarcell arrays.

SUMMARY

To overcome the limitations in the prior art described above, and toovercome other limitations that will become apparent upon reading andunderstanding the present specification, the present disclosuredescribes a structure, method and solar cell panel, comprised of asubstrate for solar cells, wherein the substrate is configured suchthat: an area of the substrate remains exposed when at least one solarcell having at least one cropped corner that defines a corner region isattached to the substrate; one or more electrical connections for thesolar cell are made in the corner region resulting from the croppedcorner of the solar cell; and at least one of the electricalconnections, connecting a first interconnect in a first location, isrepaired by connecting a second interconnect in a second location in theat least one of the electrical connections different from the firstlocation.

The second location is adjacent the first location.

An area of the at least one of the electrical connections is largeenough to encompass both the first and second locations.

The area of the at least one of the electrical connections is largeenough for electrical current to flow around the first location.

The first interconnect in the first location is removed, wherein a jointremains when the first interconnect is removed.

The area of the substrate that remains exposed includes one or morecorner conductors.

The at least one of the electrical connections is repaired by forming athird interconnect in a third location in the at least one of theelectrical connections different from the first location.

DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIGS. 1 and 2 illustrate conventional structures for solar cell panels.

FIGS. 3A and 3B illustrate an improved structure for a solar cell panel,according to one example.

FIGS. 4A and 4B illustrate an alternative structure for the solar cellpanel, according to one example.

FIG. 5 illustrates the front side of an exemplary solar cell that may beused in the improved solar cell panel of FIGS. 3A-3B and 4A-3B.

FIG. 6 illustrates the back side of the exemplary solar cell of FIG. 5.

FIG. 7 illustrates cells arranged into the 2D grid of the array,according to one example.

FIG. 8 illustrates an example of the array where one or more bypassdiodes are added to the exposed area of the substrate in the cornerregions.

FIG. 9 illustrates an example where the bypass diode is applied to theback side of the cell, with an interconnect or contact for the bypassdiode extending into the corner region between front and back contacts.

FIG. 10 illustrates a front side view of the example of FIG. 9, with theinterconnect or contact for the bypass diode extending into the cornerregion between the front and back contacts.

FIG. 11 illustrates the cells of FIGS. 9 and 10 arranged into the 2Dgrid of the array and applied to the substrate, where the bypass diodesare applied to the back side of the cells, with the contacts for thebypass diodes extending into the corner regions of the cells.

FIG. 12 shows up/down series connections between the cells of the array,according to one example.

FIG. 13 shows left/right series connections between the cells of thearray, according to one example.

FIG. 14 illustrates a connection scheme between a plurality of solarcells of an array, according to one example.

FIG. 15 shows a side view of an example wherein the substrate is a flexsheet assembly, according to one example.

FIG. 16 illustrates an example where a metal foil interconnect from asolar cell has separated from a connection pad, according to oneexample.

FIG. 17 shows one proposed repair process for the example of FIG. 16,wherein an area of the connection pad is large enough that a secondconnection can be made by a metal foil interconnect, according to oneexample.

FIG. 18 shows how the repair components are used, in one example.

FIG. 19 describes a method of fabricating a solar cell, solar cell paneland/or satellite, according to one example.

FIG. 20 illustrates a resulting satellite having a solar cell panelcomprised of solar cells, according to one example.

FIG. 21 is an illustration of the solar cell panel in the form of afunctional block diagram, according to one example.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings which form a part hereof, and in which is shown by way ofillustration a specific example in which the disclosure may bepracticed. It is to be understood that other examples may be utilizedand structural changes may be made without departing from the scope ofthe present disclosure.

General Description

A new approach to the design of solar cell arrays, such as those usedfor spaceflight power applications, is based on electrical connectionsamong the solar cells in the array.

This new approach rearranges the components of a solar cell and thearrangements of the solar cells in the array. Instead of having solarcells connected into long linear strings and then assembled onto asubstrate, the solar cells are attached individually to a substrate,such that corner regions of adjacent cells are aligned on the substrate,thereby exposing an area of the substrate. Electrical connectionsbetween cells are made by corner conductors formed on or in thesubstrate in these corner regions. Consequently, this approach presentsa solar cell array design based on individual cells.

Thus, a single laydown process and layout can be used in the fabricationof solar cell arrays. Current flow between solar cells will be assistedwith conductors embedded in the substrate. These electrical connectionsdefine the specific characteristics of the solar cell array, such as itsdimensions, stayout zones, and circuit terminations. This approachsimplifies manufacturing, enables automation, and reduces costs anddelivery times.

FIGS. 1 and 2 illustrate conventional structures for solar cell panels10, which include a substrate 12, a plurality of solar cells 14 arrangedin an array, and electrical connectors 16 between the solar cells 14.Half size solar cells 14 are shown in FIG. 1 and full size solar cells14 are shown in FIG. 2. Space solar cells 14 are derived from a roundGermanium (Ge) substrate starting material, which is later fabricatedinto semi-rectangular shapes to improve dense packing onto the solarcell panel 10. This wafer is often diced into one or two solar cells 14herein described as half size or full size solar cells 14. Theelectrical connectors 16 providing electrical connections between solarcells 14 are made along the long parallel edge between solar cells 14.These series connections (cell-to-cell) are completed off-substrate, asstrings of connected solar cells 14 are built having lengths of anynumber of solar cells 14. The completed strings of solar cells 14 arethen applied and attached to the substrate 12.

In FIG. 2, wiring 18 is attached at the end of a string of solar cells14 to electrically connect the string to other strings, or to terminatethe resulting circuit and bring the current off of the array of solarcells 14. String-to-string and circuit termination connections aretypically done on the substrate 12, and typically using wiring 18.However, some solar cell panels 10 use a printed circuit board(PCB)-type material with embedded conductors.

Adjacent strings of connected solar cells 14 can run parallel oranti-parallel. In addition, strings of connected solar cells 14 can bealigned or misaligned. There are many competing influences to the solarcell 14 layout resulting in regions where solar cells 14 are parallel oranti-parallel, aligned or misaligned.

FIGS. 3A and 3B illustrate improved devices and structures for a solarcell panel 10 a, according to one example, wherein FIG. 3B is anenlarged view of the details in the dashed circle in FIG. 3A. Thevarious components of the solar cell panel 10 a are shown and describedin greater detail in FIGS. 5-13.

The solar cell panel 10 a includes a substrate 12 for solar cells 14having one or more corner conductors 20 thereon. In one example, thesubstrate 12 is a multi-layer substrate 12 comprised of one or moreKapton® (polyimide) layers separating one or more patterned metallayers. The substrate 12 may be mounted on a large rigid panel 10 asimilar to conventional assembles. Alternatively, the substrate 12 canbe mounted to a lighter more sparse frame or panel 10 a for mounting ordeployment.

A plurality of solar cells 14 are attached to the substrate 12 in atwo-dimensional (2-D) grid of an array 22. In this example, the array 22is comprised of ninety-six (96) solar cells 14 arranged in four (4) rowsby twenty-four (24) columns, but it is recognized that any number ofsolar cells 14 may be used in different implementations.

The solar cells 14 have cropped corners 24 that define corner regions26, as indicated by the dashed circle. The solar cells 14 are attachedto the substrate 12, such that corner regions 26 of adjacent ones of thesolar cells 14 are aligned, thereby exposing an area 28 of the substrate12. The area 28 of the substrate 12 that is exposed includes one or moreof the corner conductors 20, and one or more electrical connectionsbetween the solar cells 14 and the corner conductors 20 are made in thecorner regions 26 resulting from the cropped corners 24 of the solarcells 14.

In this example, the corner conductors 20 are conductive paths attachedto, printed on, buried in, or deposited on the substrate 12, beforeand/or after the solar cells 14 are attached to the substrate 12, whichfacilitate connections between adjacent solar cells 14. The connectionsbetween the solar cells 14 and the corner conductors 20 are made afterthe solar cells 14 have been attached to the substrate 12.

In one example, four adjacent solar cells 14 are aligned on thesubstrate 12, such that four cropped corners 24, one from each solarcell 14, are brought together at the corner regions 26. The solar cells14 are then individually attached to the substrate 12, wherein the solarcells 14 are placed on top of the corner conductors 20 to make theelectrical connection between the solar cells 14 and the cornerconductors 20.

The solar cells 14 may be applied to the substrate 12 as CIC (cell,interconnect and coverglass) units. Alternatively, bare solar cells 14may be assembled on the substrate 12, and then interconnects applied tothe solar cells 14, followed by the application of a single solar cell14 coverglass, multiple solar cell 14 coverglass, multiple cell polymercoversheet, or spray encapsulation. This assembly protects the solarcells 14 from damage that would limit performance.

FIGS. 4A and 4B illustrate an alternative structure for the solar cellpanel 10 a, according to one example, wherein FIG. 4B is an enlargedview of the details in the dashed circle in FIG. 4A. In this example,only a few corner conductors 20 are printed on or integrated with thesubstrate 12. Instead, most of the corner conductors 20 are containedwithin a power routing module (PRM) 30 that is attached to the substrate12.

FIG. 5 illustrates the front side of an exemplary solar cell 14 that maybe used in the improved solar cell panel 10 a of FIGS. 3A-3B and 4A-4B.The solar cell 14, which is a CIC unit, is a half-size solar cell 14.(Full-size solar cells 14 could also be used.)

The solar cell 14 is fabricated having at least one cropped corner 24that defines a corner region 26, as indicated by the dashed circle, suchthat the corner region 26 resulting from the cropped corner 24 includesat least one contact 32, 34 for making an electrical connection to thesolar cell 14. In the example of FIG. 5, the solar cell 14 has twocropped corners 24, each of which has both a front contact 32 on thefront side of the solar cell 14 and a back contact 34 on a back side ofthe solar cell 14, where the contacts 32 and 34 extend into the cornerregion 26. (Full-size solar cells 14 would have four cropped corners 24,each of which would have a front contact 32 and a back contact 34.)

The cropped corners 24 increase utilization of the round wafer startingmaterials for the solar cells 14. In conventional panels 10, thesecropped corners 24 would result in unused space on the panel 10 afterthe solar cells 14 are attached to the substrate 12. The new approachdescribed in this disclosure, however, utilizes this unused space.Specifically, metal foil interconnects, comprising the corner conductors20, front contacts 32 and back contacts 34, are moved to the cornerregions 26. In contrast, existing CICs have interconnects attached tothe solar cell 14 front side, and connect to the back side (whereconnections occur) during stringing.

The current generated by the solar cell 14 is collected on the frontside of the solar cell 14 by a grid 36 of thin metal fingers 38 andwider metal bus bars 40 that are connected to both of the front contacts32. There is a balance between the addition of metal in grid 36, whichreduces the light entering the solar cell 14 and its output power, andthe reduced resistance of having more metal. The bus bar 40 is a lowresistance conductor that carries high currents and also providesredundancy should a front contact 32 become disconnected. Optimizationgenerally desires a short bus bar 40 running directly between the frontcontacts 32. Having the front contact 32 in the cropped corner 24results in moving the bus bar 40 away from the perimeter of the solarcell 14. This is achieved while simultaneously minimizing the bus bar 40length and light obscuration. Additionally, the fingers 38 are nowshorter. This reduces parasitic resistances in the grid 36, because thelength of the fingers 38 is shorter and the total current carried isless. This produces a design preference where the front contacts 32 andconnecting bus bar 40 is moved to provide shorter narrow fingers 38.

FIG. 6 illustrates the back side of the exemplary solar cell 14 of FIG.5. The back side of the solar cell 14 has a metal back layer 42 that isconnected to both of the back contacts 34.

FIG. 7 illustrates solar cells 14 arranged into the 2D grid of the array22, according to one example. The array 22 comprises a plurality ofsolar cells 14 attached to a substrate 12, such that corner regions 26of adjacent ones of the solar cells 14 are aligned, thereby exposing anarea 28 of the substrate 12. Electrical connections (not shown) betweenthe solar cells 14 are made in the exposed area 28 of the substrate 12using the front contacts 32 and back contacts 34 of the solar cells 14and corner conductors 20 (not shown) formed on or in the exposed area 28of the substrate 12.

During assembly, the solar cells 14 are individually attached to thesubstrate 12. This assembly can be done directly on a support surface,i.e., the substrate 12, which can be either rigid or flexible.Alternatively, the solar cells 14 could be assembled into the 2D grid ofthe array 22 on a temporary support surface and then transferred to afinal support surface, i.e., the substrate 12.

FIG. 8 illustrates an example of the array 22 where one or more bypassdiodes 44 are added to the exposed area 28 of the substrate 12 in thecorner regions 26, for use in one or more of the electrical connections.The bypass diodes 44 protect the solar cells 14 when the solar cells 14become unable to generate current, which could be due to being partiallyshadowed, which drives the solar cells 14 into reverse bias. In oneexample, the bypass diodes 44 are attached to the substrate 12 in thecorner regions 26 independent of the solar cells 14.

FIG. 9 illustrates an example where the bypass diode 44 is applied tothe back side of the solar cell 14, with interconnects or contacts 46for the bypass diode 44 connected to the back layer 42 and alsoextending into the corner region 26 between the front and back contacts32, 34.

FIG. 10 illustrates a front side view of the example of FIG. 9, with theinterconnect or contact 46 for the bypass diode 44 (not shown) extendinginto the corner region 26 between the front and back contacts 32, 34.

FIG. 11 illustrates the solar cells 14 of FIGS. 9 and 10 arranged intothe 2D grid of the array 22 and applied to the substrate 12, where thebypass diodes 44 (not shown) are applied to the back side of the solarcells 14, with the contacts 46 for the bypass diodes 44 extending intothe corner regions 26 of the solar cells 14.

One advantage of this approach is that the layouts illustrated in FIGS.7, 8 and 11 are generalized layouts. Specifically, these layouts can berepeated across any panel 10 a dimensions desired by a customer. Thisgreatly simplifies assembly, rework, test, and inspection processes.

The placement of the solar cell 14 and bypass diode 44 is generic Theelectrical connection of the solar cells 14 into series connections andstring terminations is important customization for the end customer andis done independent of the layout. The front contacts 32 and backcontacts 34 in the corner regions 26 of the solar cells 14 must beconnected. This can be done in many combinations in order to routecurrent through a desired path.

Connections are made between the solar cells 14 and the cornerconductors 20. Front and back contacts 32, 34 of the solar cells 14 arepresent in each corner region 26 for attachment to the corner conductors20. Interconnects for the front and back contacts 32, 34 of each of thesolar cells 14 are welded, soldered, or otherwise bonded onto the cornerconductors 20 to provide a conductive path 20, 32, 34 for routingcurrent out of the solar cells 14.

Using the corner conductors 20, any customization can be made in theelectrical connections. Adjacent solar cells 14 can be electricallyconnected to flow current in up/down or left/right directions as desiredby the specific design. Current flow can also be routed around stay-outzones as needed. The length or width of the solar cell array 22 can beset as desired. Also, the width can vary over the length of the array22.

In one example, the electrical connections are series connections thatdetermine a flow of current through the plurality of solar cells 14.This may be accomplished by the connection schemes shown in FIGS. 12 and13, wherein FIG. 12 shows up/down series connections 48 between thesolar cells 14 of the array 22, and FIG. 13 shows left/right seriesconnections 50 between the solar cells 14 of the array 22. In both FIGS.12 and 13, these series connections 48, 50 are electrical connectionsbetween the front contacts 32 and back contacts 34 of the solar cells14, and the bypass diodes 44, are made using the corner conductors 20formed on or in the exposed areas 28 of the substrate 12. These seriesconnections 48, 50 determine the current (power) flow, as indicated bythe arrows 52, through the solar cells 14.

The corner conductors 20 between solar cells 14 can be in many forms.They could be accomplished using wires that have electrical connectionsmade on both ends, which could be from soldering, welding, conductingadhesive, or other process. In addition to wires, metal foil connectors,similar to the interconnects could be applied. Metal conductive paths ortraces (not shown) can also be integrated with the substrate 12.

In summary, this new approach attaches the solar cells 14 individuallyto a substrate 12 such that the corner regions 26 of two, three or fouradjacent solar cells 14 are aligned on the substrate 12. The solar cells14 can be laid out so that the cropped corners 24 are aligned and thecorner regions 26 are adjacent, thereby exposing an area 28 of thesubstrate 12. Electrical connections between solar cells 14 are made inthese corner regions 26 between front contacts 32 and back contacts 34on the solar cells 14, bypass diodes 44, and corner conductors 20 on orin the exposed area 28 of the substrate 12, wherein these conductivepaths are used to create a string of solar cells 14 in a seriesconnection 48, 50 comprising a circuit.

Rework and Repair of Components

While the use of electrical connections between solar cells 14 in thesecorner regions 26 facilitates automation, there are limits to the reworkand repair capabilities of this design. Solar cell arrays 22 go throughmuch activity before deployment, and there are numerous chances fordefects both in early manufacture and during later assembly stages,however rare. It is necessary to have a path for rework and repair toreplace damaged materials.

Specifically, a rework and repair process is necessary for the 2D gridof the array 22, and it is not clear how that is achieved using existingtechniques. For example, the extraction and replacement of componentsmay result in a second electrical interconnect made in the same locationas a first electrical interconnect, and such a repeated connection maynot have sufficient strength.

This disclosure describes a connector design that simplifies rework ofthese items, and facilitates repairs of the solar cell array 22.Specifically, an electrical connection is repaired by removing a firstinterconnect in a first location in the electrical connection and byforming a second interconnect in a second location in the electricalconnection different from the first location. The second location may beadjacent the first location, for example, when an area used for theelectrical connection is large enough to encompass both the first andsecond locations and to allow electrical current to flow around thefirst location.

FIG. 14 further illustrates a connection scheme between a plurality ofsolar cells 14, according to one example. The connection scheme showncomprises up/down series connections 48 between the front contacts 32and back contacts 34 of the solar cells 14, and the bypass diodes 44,made in the exposed areas 28 of the substrate 12, using the cornerconductors 20. These series connections 48 determine the flow ofcurrent, as indicated by the arrows 52, through the solar cells 14.

One or more conductor elements may be added to or removed from thecorner region 26 to select current pathways for the solar cells 14. Inone example, the conductor element comprises a jumper 54 a, 54 b thatallows circuits to be terminated at the corner regions 26 or to directcurrent to the next solar cell 14. The jumpers 54 a, 54 b bridge theelectrical connections from at least one of the corner conductors 20 toone or more other conductive paths.

Each jumper 54 a, 54 b is a metal foil interconnect that is similar toexisting metal interconnects used in solar cell panels 10. In oneexample, each jumper 54 a, 54 b has a shape comprised of two flangeelements with parallel planes connected by a web element, which enablesmultiple connection points. The jumper 22 could be welded, soldered, orjoined by other methods, onto the conducting paths and connection pads.Other types of conductive elements, such as wires, as well as othershapes, could also be employed.

Specifically, FIG. 14 shows a jumper 54 a that connects the back contact34 of the top left solar cell 14 to the front contact 32 of the bottomleft solar cell 14. This jumper 54 a also connects through the bypassdiode 44 to the back contact 34 of the bottom left solar cell 14. Thisconnection path provides for the current flow 52 from top to bottomshown on the left side of the figure. A similar configuration usingjumper 54 b provides for the current flow 52 from bottom to top shown onthe right side of the figure.

The value of this structure is significant. Now, there is a singleprinted corner conductor 20 pattern, single layout of solar cells 14,and single layout of bypass diodes 44. This single configuration hasgreat advantages for automation of manufacturing, testing, andinspection. The application of a jumper 54 a, 54 b provides for a simpleway to control the number of solar cells 14 in a circuit.

FIG. 15 shows a side view of an example wherein the substrate 12 is aflex sheet assembly, according to one example. The substrate 12 includesa polyimide base layer 54 with Copper (Cu) layer 56 a above and Cu layer56 b below, wherein Cu layers 56 a and 56 b form a multilayer conductor.A conducting back sheet of polyimide 58 can be applied to the substrate12, which is useful in a space environment in that it will reduce theaccumulation of charge. Another capability is the addition of a platedSilver (Ag) or Gold (Au) layer 60 on the Cu layer 56 a, which improvesthe ability to make connections. The Cu layer 56 a with plated Ag or Aulayer 60 is patterned as the corner conductors 20, and the Cu layer 56 bis patterned to form buried conductors within the substrate 12,including, for example, power and common lines.

Shown on the right side is the solar cell 14 that is attached to thesubstrate 12 with adhesive 62. Also visible is the metal foilinterconnect 64 attached to the solar cell 14 and the plated Ag or Aulayer 60 of the corner conductors 20. This is a rather typicalconstruction and assembly that could form the structures presented inearlier figures.

The substrate 12 also includes insulating layers that separate at leastone of the multilayer conductors 56 a, 56 b from at least another one ofthe multilayer conductors 56 a, 56 b. In one example, there are a toppolyimide overlay layer 66 a and bottom polyimide overlay layer 66 b,wherein the top Polyimide overlay layer 66 a has one or more holesdrilled through it, and the holes are Cu-plated vias 68 thatelectrically connect Cu layer 56 a with Cu layer 56 b.

Polyimide has a high breakdown strength, greater than air or vacuum, andthe polyimide overlay layers 66 a, 66 b are useful for preventingelectrostatic discharge (ESD), which is an important concern in thespace environment. Furthermore, this enables corner conductors 20 topass under the solar cell 14. The adhesive 62 is non-conducting, but thecontinuous polyimide layer of the polyimide overlay layers 66 a, 66 boffers significant protection against shorting between buried conductorsin Cu layers 56 a, 56 b and the solar cell 14.

In another example, the top polyimide overlay layer 66 a may be omittedunderneath the solar cell 14. This may be advantageous if the toppolyimide overlay layer 66 a is prone to bubbles or other defects.

In another example, there is an alignment between Cu layer 56 a, Culayer 56 b and the top polyimide overlay layer 66 a. In this example,the top polyimide overlay layer 66 a almost fully encases the Cu layer56 a, polyimide layer 54, and Cu layer 56 b, with only small accessholes to the Cu layer 56 a and Cu layer 56 b. This requires the toppolyimide overlay layer 66 a to roll up and over the corners of the Culayers 56 a and 56 b. By encasing the metal of the Cu layers 56 a, 56 b,the top polyimide overlay layer 66 a provides valuable protectionagainst ESD.

In another example, the top polyimide overlay layer 66 a has largerholes to avoid overlapping the edges of the Cu layers 56 a and 56 b.This top polyimide overlay layer 66 a may be easier to fabricate withless defects than a full top polyimide overlay layer 66 a.

In another example, there is a connection between two or more traces ofthe Cu layer 56 a, wherein the traces of the Cu layer 56 a are alsoconnected by vias 68 to Cu layer 56 b. The top polyimide overlay layer66 a may not be needed; in that case, there would be no hindrance of thetop polyimide overlay layer 66 a to any jumper 54 connection.

In another example, a jumper 54 (not shown) may connect directly fromthe Cu layer 56 a to the Cu layer 56 b. This eliminates the Cu-platedvia 68 connections, which could be a reliability concern, especially inthe flex sheet assembly. However, there is more polyimide topographyfrom the top polyimide overlay layer 66 a that the jumper 54 needs toreach over. The thickness of the top polyimide overlay layer 66 a istypically about ˜0.1 mm, while the length of the jumper 54 typically maybe about ˜4 mm. Having the metal of the jumper 54 surrounded by largeamounts of polyimide from the top polyimide overlay layer 66 a mayimpede the jumper 54, but will also impede ESD, which can be valuable.

In another example, electrical access is provided to the buried Cu layer56 b. This could be accomplished with the via 68 connection between Culayer 56 a and Cu layer 56 b, or with a direct connection between Culayer 56 a and Cu layer 56 b. Also, there may be multiple connectionsbetween Cu layer 56 a and Cu layer 56 b. This redundancy is an importantattribute and can be employed when possible.

In another example, the traces of the Cu layers 56 a, 56 b can bebroadened into wider conductors, power lines and common lines that donot have the insulating polyimide layers 66 a, 66 b between them. Thus,there is more Copper used for conduction, which reduces resistancelosses. This does reduce the number of discrete conductors; however, theconnection redundancy is preserved.

If there is a problem with the solar cell 14 or its connections, theymay need to be replaced. Mechanical removal of the solar cell 14 and theadhesive 62 attaching it to the surface of the flex sheet substrate 12is a known process. This disclosure, on the other hand, is focused onreworking or repairing the electrical connections.

FIG. 16 illustrates an example where the metal foil interconnect 64 fromthe solar cell 14 has separated from the plated Ag or Au layer 60 and/orCu layer 56 a. This separation may be the defect causing the reworkprocess. Alternatively, there could be another defect causing thisconnection to be purposely separated. For example, a cracked solar cell14 would need to be removed including the interconnections to thesubstrate 12. The separation results in a change in the surface regionof the plated Ag or Au layer 60 and/or Cu layer 56 a, for example,resulting in some debris 70, such as solder residue, roughness, etc.

FIG. 17 shows one proposed process for repairing the substrate 12 in theexample of FIG. 16, wherein an area of the plated Ag or Au layer 60and/or Cu layer 56 a used for the electrical connection is large enoughthat one or more additional connections can be made in the area In thisexample, the replacement solar cell 14 is attached to the flex sheetsubstrate 12 using adhesive 62, and the replacement interconnect 64extends from the replacement solar cell 14 to make contact with theplated Ag or Au layer 60 and/or Cu layer 56 a in an adjacent locationthat avoids the original connection region. The adjacent location inthis example has enough conductor for electrical current to flow aroundthe damaged region.

There could be an inventory of CICs with different length interconnectsfor first assembly, first rework, second rework, etc. Alternatively, asingle CIC could be built with an interconnect having a length availablefor initial assembly and all anticipated rework processes.

Specifically, an electrical connection is repaired by removing a firstinterconnect 64 in a first location in the electrical connection and byforming a second interconnect 64 in a second location in the electricalconnection different from the first location. The second location may beadjacent the first location, for example, when the plated Ag or Au layer60 and/or Cu layer 56 a comprise a connection pad that is large enoughto encompass both the first and second locations and to allow electricalcurrent to flow around the first location. In one example, the firstinterconnect 64 in the first location is completely removed, while inanother example, a joint remains when the first interconnect 64 isremoved.

In another proposed repair process, similar to that shown in FIG. 17,the area of the plated Ag or Au layer 60 and/or Cu layer 56 a has beenruptured or divoted. Like FIG. 17, a replacement solar cell 14 isattached to the flex sheet substrate 12 using adhesive 62, and areplacement interconnect 64 extends from the replacement solar cell 14to make contact with the plated Ag or Au layer 60 and/or Cu layer 56 ain an adjacent location that avoids the original connection region,wherein the adjacent location has enough conductor for electricalcurrent to flow around the damaged region.

In another proposed repair process, wherein the original interconnect 64to the solar cell 14 is cut, but a joint of the interconnect 64 remainsintact and bonded to the plated Ag or Au layer 60 and/or Cu layer 56 a,a replacement interconnect 64 is attached to the plated Ag or Au layer60 and/or Cu layer 56 a in an adjacent location that avoids the originalconnection region, wherein the adjacent location has enough conductorfor electrical current to flow around the joint of the interconnect 64.Maintaining the joint of the interconnect 64 may be preferred as thisavoids damage to the plated Ag or Au layer 60 and/or Cu layer 56 a, forexample, by rupturing or divoting.

Different types of repair components may be used, based on two types ofinterconnects. A first type of repair components could be used inconnecting a solar cell 14 or bypass diode 44 to the substrate 12, whilea second type of repair components could be used to connect pairs ofcorner conductors 20 on the substrate 12. The first type of repaircomponents would be the standard interconnects 64, while the second typeof repair components would be variations of the standard interconnects64 used for the repair process, i.e., replacement interconnects 64,which have a slightly different structure that moves the electricalconnection to an adjacent location from the original connection. It isdesirable to position the initial and rework connection points, suchthat debris 70, cut interconnect 64, or rupturing or divoting of theplated Ag or Au layer 60 and/or Cu layer 56 a, does not impact repairassembly or current flow.

Another variation is where the type of repair components is designed toallow initial and rework connections to be made using the sameinterconnect 64 structure. Thus, a single interconnect 64 is needed.This interconnect 64 is used for both the initial build and for rework.There would be initial and rework pairs of connection points on theplated Ag or Au layer 60 and/or Cu layer 56 a for the initial and reworkconnections. Again, it is desirable to design these parts and theconducting path on the substrate 12, such that rupture of the conductingpath on the substrate 12 does not impact conductivity after rework.

In the case where a connection point is inadequate, this interconnectdesign enables an additional connection point to be used. Theinterconnect 64 can be left in place and an adjacent location of theplated Ag or Au layer 60 and/or Cu layer 56 a can be used to providegreater reliability. This avoids the possibility of further damageduring the rework process.

FIG. 18 shows how repair components 72 are used, according to oneexample. In this example, the repair components 72 comprise replacementinterconnects 64 connecting the front or back contacts 32, 34 to thecorner conductors 20, or replacement interconnects 64 connecting thebypass diodes 44 to the corner conductors 20, or jumpers 54 connectingthe corner conductors 20. Generally, the following steps are performed:separate interconnects 64 at a weld joint, clean out the solar cell 14and/or bypass diode 44, replace the solar cell 14 and/or bypass diode 44with a repair unit, and weld the interconnects 64 at adjacent locationsto the corner conductors 20 or front and back contacts 32, 34, orconnect a jumper 54 between corner conductors 20, wherein all work isperformed on a top side of the assembly with no components sticking up.

Preferably, all the electrical connections in this assembly are made byoverlapping metal layers. Then, a joint is formed by access from the topfor solder or weld processes (laser, resistive, ultrasonic, etc.). Thisaccess is very straightforward, as there is no overlapping or folding ofconductors. Also, the repair has no material sticking up higher than theoriginal assembly, which is a concern for space solar panels 10 a thatare often folded tightly for stowage and launch.

Fabrication

Examples of the disclosure may be described in the context of a method74 of fabricating a solar cell 14, solar cell panel 10 a and/orsatellite, comprising steps 76-88, as shown in FIG. 19, wherein theresulting satellite 90 having a solar cell panel 10 a comprised of solarcells 14 are shown in FIG. 20.

As illustrated in FIG. 19, during pre-production, exemplary method 74may include specification and design 76 of the solar cell 14, solar cellpanel 10 a and/or satellite 90, and material procurement 78 for same.During production, component and subassembly manufacturing 80 and systemintegration 82 of the solar cell 14, solar cell panel 10 a and/orsatellite 90 takes place, which include fabricating the solar cell 14,solar cell panel 10 a and/or satellite 90. Thereafter, the solar cell14, solar cell panel 10 a and/or satellite 90 may go throughcertification and delivery 84 in order to be placed in service 86. Thesolar cell 14, solar cell panel 10 a and/or satellite 90 may also bescheduled for maintenance and service 88 (which includes modification,reconfiguration, refurbishment, and so on), before being launched.

Each of the processes of method 74 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of solar cell, solar cell panel, satelliteor spacecraft manufacturers and major-system subcontractors; a thirdparty may include without limitation any number of venders,subcontractors, and suppliers; and an operator may be a satellitecompany, military entity, service organization, and so on.

As shown in FIG. 20, a satellite 90 fabricated by exemplary method 74may include systems 92, a body 94, solar cell panels 10 a comprised ofsolar cells 14, and one or more antennae 96. Examples of the systems 92included with the satellite 90 include, but are not limited to, one ormore of a propulsion system 98, an electrical system 100, acommunications system 102, and a power system 104. Any number of othersystems 92 also may be included.

FIG. 21 is an illustration of the solar cell panel 10 a in the form of afunctional block diagram, according to one example. The solar cell panel10 a is comprised of the solar cell array 22, which is comprised of oneor more of the solar cells 14 individually attached to the substrate 12.Each of the solar cells 14 absorbs light 106 from a light source 108 andgenerates an electrical output 110 in response thereto.

At least one of the solar cells 14 has at least one cropped corner 24that defines a corner region 26, such that an area 28 of the substrate12 remains exposed when the solar cell 14 is attached to the substrate12. When a plurality of solar cells 14 are attached to the substrate 12,the corner regions 26 of adjacent ones of the solar cells 14 arealigned, thereby exposing the area 28 of the substrate 12.

The area 28 of the substrate 12 that remains exposed includes one ormore corner conductors 20 attached to, printed on, or integrated withthe substrate 12, and one or more electrical connections between thesolar cells 14 and the corner conductors 20 are made in a corner region26 resulting from the cropped corner 24 of the at least one of the solarcells 14.

The corner region 26 resulting from the cropped corner 24 includes atleast one contact, for example, a front contact 32 on a front side ofthe solar cell 14 and/or a back contact 34 on a back side of the solarcell 14, for making the electrical connections between the cornerconductors 20 and the solar cell 14. The electrical connections maycomprise up/down or left/right series connections that determine a flowof power through the solar cells 14, and may include one or more bypassdiodes 44.

The description of the examples set forth above has been presented forpurposes of illustration and description, and is not intended to beexhaustive or limited to the examples described. Many alternatives,modifications and variations may be used in place of the specificelements described above.

What is claimed is:
 1. A structure, comprising: a substrate for solarcells, wherein the substrate is configured such that: an area of thesubstrate remains exposed when at least one solar cell having at leastone cropped corner that defines a corner region is attached to thesubstrate; one or more electrical connections for the solar cell aremade in the corner region resulting from the cropped corner of the solarcell; and at least one of the electrical connections, connecting a firstinterconnect in a first location, is repaired by connecting a secondinterconnect in a second location in the at least one of the electricalconnections different from the first location.
 2. The structure of claim1, wherein the second location is adjacent the first location.
 3. Thestructure of claim 1, wherein an area of the at least one of theelectrical connections is large enough to encompass both the first andsecond locations.
 4. The structure of claim 3, wherein the area of theat least one of the electrical connections is large enough forelectrical current to flow around the first location.
 5. The structureof claim 1, wherein the first interconnect in the first location isremoved.
 6. The structure of claim 5, wherein a joint remains when thefirst interconnect is removed.
 7. The structure of claim 1, wherein thearea of the substrate that remains exposed includes one or more cornerconductors.
 8. The structure of claim 1, wherein the at least one of theelectrical connections is repaired by forming a third interconnect in athird location in the at least one of the electrical connectionsdifferent from the first location.
 9. A method, comprising: repairing asubstrate for solar cells, wherein the substrate is configured suchthat: an area of the substrate remains exposed when at least one solarcell having at least one cropped corner that defines a corner region isattached to the substrate; one or more electrical connections for thesolar cell are made in the corner region resulting from the croppedcorner of the solar cell; and at least one of the electricalconnections, connecting a first interconnect in a first location, isrepaired by connecting a second interconnect in a second location in theat least one of the electrical connections different from the firstlocation.
 10. The method of claim 9, wherein the second location isadjacent the first location.
 11. The method of claim 9, wherein an areaof the at least one of the electrical connections is large enough toencompass both the first and second locations.
 12. The method of claim11, wherein the area of the at least one of the electrical connectionsis large enough for electrical current to flow around the firstlocation.
 13. The method of claim 9, wherein the first interconnect inthe first location is removed.
 14. The method of claim 13, wherein ajoint remains when the first interconnect is removed.
 15. The method ofclaim 9, wherein the area of the substrate that remains exposed includesone or more corner conductors.
 16. The method of claim 9, wherein the atleast one of the electrical connections is repaired by forming a thirdinterconnect in a third location in the at least one of the electricalconnections different from the first location.
 17. A solar cell panel,comprising: a solar cell array comprised of at least one solar cellhaving at least one cropped corner that defines a corner region and asubstrate for the solar cell, wherein the substrate is configured suchthat: an area of the substrate remains exposed when at least one solarcell having at least one cropped corner that defines a corner region isattached to the substrate; one or more electrical connections for thesolar cell are made in the corner region resulting from the croppedcorner of the solar cell; and at least one of the electricalconnections, connecting a first interconnect in a first location, isrepaired by connecting a second interconnect in a second location in theat least one of the electrical connections different from the firstlocation.
 18. The solar cell panel of claim 17, wherein the secondlocation is adjacent the first location.
 19. The solar cell panel ofclaim 17, wherein an area of the at least one of the electricalconnections is large enough to encompass both the first and secondlocations.
 20. The solar cell panel of claim 19, wherein the area of theat least one of the electrical connections is large enough forelectrical current to flow around the first location.
 21. The solar cellpanel of claim 17, wherein the first interconnect in the first locationis removed.
 22. The solar cell panel of claim 21, wherein a jointremains when the first interconnect is removed.
 23. The solar cell panelof claim 17, wherein the area of the substrate that remains exposedincludes one or more corner conductors.
 24. The solar cell panel ofclaim 17, wherein the at least one of the electrical connections isrepaired by forming a third interconnect in a third location in the atleast one of the electrical connections different from the firstlocation.